An ever-increasing number of research studies have found, however, that there is no evidence to support Sessions' claims, as legal weed is actually associated with decreases in violent crime. The latest of these studies, published in the Journal of Economic Behavior & Organization, examined crime rates in several counties close to the Washington/Oregon border between 2010 and 2014. The researchers especially focused on the years of 2012 to 2014, where recreational marijuana was legal in Washington, but not yet legal in Oregon.

The study reports that the legalization of marijuana in Washington "caused a significant reduction in rapes and property crimes on the Washington side of the border in 2013–2014 relative to the Oregon side and relative to the pre-legalization years 2010–2012." These reductions were quite significant, with Washington counties reporting between 15 and 30% fewer rapes and 10 to 20% fewer property crimes.

The study reported seeing an increase in cannabis consumption after the drug was legalized, but this was associated with a decrease in the use of illegal drugs, as well as both binge drinking and regular alcohol use. The nature of the study does not provide any specific explanation why legalization could lead to less crime, but the authors offered several theories, including the possibility that local police had more time to focus on stopping actual dangerous crime since they were no longer busy enforcing cannabis prohibition laws.

The researchers also considered the possibility that the "state of relaxation and euphoria" created by smoking weed "reduces the likelihood of engaging in violent activities," the Pacific Standard reports. Another possible explanation offered was that the decrease in use of alcohol and other "violence-inducing" drugs like speed or cocaine was responsible for the decrease in violence. A fourth explanation was that legalization "may have reduced the role of criminal gangs and small criminals in local cannabis markets."

The research team concluded that "the concern that legalizing cannabis for recreational purposes may increase crime occupies a prominent position in the public debate about drugs," NORML reports. "Our analysis suggests that such a concern is not justified."